The present invention relates to a tubular belt conveyor constructed so as to prevent a tubular endless belt for conveying objects to be conveyed such as powdered/grained objects or pieces in a wrapped-in state from being sagged and twisted during the running thereof and to reduce the number of supporting frames to promote saving.
As means for conveying the objects to be conveyed (hereinafter referred to as conveyed objects) such as the powder/grained objects or pieces to a considerably remote place, there is generally known a tubular belt conveyor of the type shown in FIGS. 7 to 9.
That is, a flexible endless belt 1 has a tendency to roll up owing to the elasticity of its own. However, the end portions thereof over driven roller 3 and drive roller 2 are unrolled into flattened form and wound round the rollers, the upper section thereof extending from the driven roller 3 toward the drive roller constitutes an outward belt 1a, while the lower section thereof extending from the drive roller 2 toward the driven roller 3 constitutes a return belt 1b, and supporting frames 4 are provided along the outward belt 1a and the return belt 1b at predetermined intervals. The individual supporting frames 4 are coupled to one another by upper, lower, right and left coupling members 8 and are divided into upper and lower parts by partition plates 4c. Passages 4a and 4b through which the belt is inserted and formed in the upper and lower parts of the frame 4. Several holding rollers 5 are provided on the periphery of each of the passages 4a and 4b via brackets 5a so as to lie along one circumference and in such a manner that portions of the outward and return belts 1a and 1b which are rolled up into tubular form can be supported by the holding rollers 5. In positions immediately after a position of the belt which runs the driven roller 3 and in positions in front of the drive roller 2, there are provided a plurality of rolling/unrolling frames 6 which are provided on upper and lower portions thereof with deformation rollers 7 for supporting three parts, that is the bottom or the upper part and the both sides of the belt.
Thus, the outward belt 1a which runs over the driven roller 3 thereunder and is unrolled into the flattened form is roller up into the tubular form owing to its tendency to roll up and with the aid of the deformation rollers 7 on the rolling/unrolling frame 6, during which an object to be conveyed (conveyed object) "m" is put on the belt from a hopper "Ha". The outward belt 1a wraps the conveyed object therein by superposing its side edge 1" on its side edge 1', passes through the upper insert passage 4a in each of the supporting frames and its again unrolled into the flattened form by the upper deformation roller on the rolling/unrolled frame 6 on the side of the drive roller in a position in which it has passed by the frontmost supporting frame 4 and the conveyed object "m" is thrown down into a receiving pipe "Hb" during the belt 1a is running over the drive roller 2.
Next, the outward belt 1a turns to the return belt 1b which is, then, rolled up by the lower deformation roller on the rolling/unrolling frame 6, passes through the lower insert passage 4b in each of the supporting frames 4, is unrolled by the lower deformation roller 7 on the rolling/unrolling frame 6 on the side of the driven roller, and then runs over the driven roller 3 to complete one cycle.
However, in the tubular belt conveyor of the aboved-mentioned type, the tubular belt is twisted along the axis thereof due to a) uneven wear of each sliding part due to the long-term use thereof, b) positional misalignment of individual holding rollers, c) uneven wear of each holding roller, d) manufacturing error in accuracy of each component, and others. Accordingly, as disclosed in Japanese Laid Open Patent Publication No. 141304/82, there has been proposed an apparatus in which as shown in FIGS. 10(a) and 10(b), a receiving plate 4d is extendingly provided behind the partition plate 4c of the supporting frame 4 and the center of a bracket 5a' for rotatably supporting a correction roller 5' which orthogonally abutes against the bottom of the outward belt 1a is pivoted on the receiving plate 4d in such a manner that in a case that the outward belt 1a is twisted, the correction roller 5' is inclined together with the bracket 5a' to the left or right with respect to a direction in which the belt runs by a handle 5d' which extends from the bracket 5a' in a lateral direction.
In the tubular belt conveyor, the twists about the axis to be generated during the running of the tubular belt occur in many and unspecific portions thereof, so that it is difficult to select in advance position in which the twist preventing means as mentioned above is set. Therefore, the twist preventing means should be provided on all of the supporting frames, which means that not only the number of the supporting frames can not be reduced but also the same number of the twist preventing means as that of the supporting frames is needed, which is very wasteful. In addition, the provision of the twist preventing means is of no use to prevent the tubular belt from being sagged.
The present invention has been contemplated in view of the above mentioned drawbacks associated with the prior art. Accordingly, an object of the present invention is to provide an economic tubular belt conveyor in which the twisting of the tubular belt can be properly corrected and the sagging of the belt between the supporting frames can also be prevented, and a space between the supporting frames can be widened, by which the number of the supporting rollers can be reduced.